Yellow Nutsedge, perennial pest

Nutsedges are common weeds in South Hampton Roads. Thriving in waterlogged soil, they are a good indicator of poor drainage, over irrigation, or leaky irrigation. Yellow nutsedge is found throughout southeastern Virginia.

Identification
Nutsedges resemble grasses, and are often referred to as “nutgrass”. They are not grasses, however but true sedges. Grasses have opposite leaves in sets of twos, whereas sedges have thicker and stiffer leaves, and are arranged in sets of three at the base. Their stems are solid and when looked at in cross sections, they are triangular. Yellow nutsedge has light brown flowers and seed.
Yellow nutsedge produces tubers which are produced on rhizomes that can grow as deep as 8-14 inches below the soil surface. These tubers bud and sprout to form new plants, eventually forming patches that can be as large as ten feet or more in diameter. These tubers are round, smooth and brown or black, and about a half inch at maturity. Only one tuber is formed at the end of each rhizome.

Life Cycle
Yellow nutsedge is a perennial. Its leaves and stems die back in the fall as temperatures decrease, with the tubers and rhizomes becoming dormant until spring, when soil temperatures remain above 43ºF. Research has indicated that most new plants are from the tubers, of which the majority can be found in the top 6 inches of soil. Seeds apparently do not contribute much to the spread of this weed.

Damage
Yellow nutsedge grows faster, has a more upright growth habit, and is lighter in color than most turfgrasses, creating the problem of non-uniform turf. Yellow nutsedge will emerge through bark or mulch in gardens or beds throughout the growing season.
Management

Limiting production of tubers is key to control of Yellow nutsedge. Tubers are necessary for survival. Remove small plants before they have five or six leaves, as new tubers have not formed at this stage. This should be done every two to three weeks. This will force the existing tubers to focus energy on new plant production as opposed to tuber production. If the weed is found in turf in small patches, it is generally best to dig out the patch to a depth of at least 8 inches, and seed or sod the patch.
Shading can be an effective way of reducing their growth. Nutsedges prefer full sun, so in landscape areas a tall dense groundcover can impede its growth.

Chemical Control

Postemergent chemical control can be handled with the use of IMAGE (Ammonium salt of imazaquin). It is best applied to young plants while the plant is still building energy reserves in the tubers. This is the time that the chemical will best be translocated to the tubers for a complete control. If the plant has past its growth stage of the 5th leaf stage, translocation will be slowed or non-existent, killing only the above ground portion. Often more than one application is necessary.

Mark Griffith is a Virginia Certified Horticulturist and a lead designer with Nautilus Garden Designs in Hampton Roads www.nautilusgardendesigns.com